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Environmental fate & pathways

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If released in water, chenodeoxycholic acid is expected to biodegrade quite quickly, according to results of the ready biodegradability test performed on the similar substance ursodeoxycholic acid. Thus, the test item, although it is not used in a detergent, can be considered a surfactant as defined in Regulation 648/2004/EC: “any organic substance and/or mixture used in detergent, which has surface-active properties and which consist of one or more hydrophilic and one or more hydrophobic groups of such a nature and size that is capable of reducing the surface tension of water, and of forming spreading or adsorption monolayers at the water-air interface, and of forming emulsions and /or microemulsions and/or micelles, and of adsorption at water-solid interfaces”. Therefore, a surfactant shall be considered as biodegradable if the level of biodegradability is at least 60% within 28 days, irrespectively from 10-day window principle. In this test, carried out according to OECD TG 301F, ursodeoxycholic acid reached 53.4% of degradation after the 10-d window, and 82% after 28 days. Therefore chenodeoxycholic acid is considered readily biodegradable.

According to the results of the abiotic degradation hydrolysis test, it can be concluded that the hydrolysis of the similar substance ursodeoxycholic acid is lower than 10% after 5 days at for the pH values 4, 7 and 9 and therefore, chenodeoxycholic acidis not expected to hydrolyze.

If released in soil, Chenodeoxycholic acid is expected to have a high mobility, according to its Koc value of 48 (logKoc: 1.69) obtained on the basis of a test performed on the similar substance ursodeoxycholic acid according to OECD TG 121 (Estimation of the Adsorption / Desorption Coefficient Koc).

Distribution of chenodeoxycholic acid into the atmosphere is not expected, based on the low estimated vapour pressure of the substance (3.00 * 10-13mmHg at 25° C).